Best Greenhouse Heaters for Winter: Questions Answered
Is it cheaper to run a fan heater or a tubular heater? Choosing a tubular heater is far cheaper in the long run, but the real question is what you’re trying to protect. The rest of this page answers the questions that determine whether that lower running cost is the right choice for your greenhouse.
Do I really need a heater in my greenhouse over winter?
While a greenhouse provides shelter from the rain, an unheated structure will still drop below freezing on cold nights. This can damage half-hardy plants like fuchsias and pelargoniums. To maintain a reliably frost-free environment for tender plants, a heater becomes necessary. For dependable frost protection, a 2kW electric heater with a thermostat is a solid choice as it prevents the unit from running unnecessarily. Full details in our guide to Best Greenhouse Heaters for Winter UK.
Finding the most affordable heating method
Electric tubular heaters are the budget-friendly option for very small greenhouses or for preventing soil in pots from freezing solid. Their running costs are minimal. The compromise is their lack of temperature control; you set their output and they run continuously. For a larger space or if you need to protect specific plants without heating the entire greenhouse, a thermostatically controlled system is essential for managing expenses. Full details in our guide to Best Greenhouse Heaters for Winter UK.
Will a fan heater keep my greenhouse frost-free?
A fan heater can provide adequate warmth, but its cost-effectiveness hinges entirely on having a thermostat. Without one, the heater may run around the clock, leading to a significant electricity bill, especially given recent price increases. The presence of a thermostat is the critical factor that separates a practical investment from a financial strain. Full details in our guide to Best Greenhouse Heaters for Winter UK.
The importance of a thermostat for plant health
Inconsistent temperature control is a leading cause of plant loss over winter. A heater that runs too hot, too cold, or cycles erratically can be just as damaging as no heat at all. A digital thermostat provides precise control, offering reliable frost protection that tender plants require. For a small, well-insulated greenhouse with only hardy plants, a manual thermostat can suffice, though it needs more frequent checking. Full details in our guide to Electric Greenhouse Heaters With Thermostat.
Selecting the right thermostat
According to RHS advice, a thermostat is key for regulating temperature for different plants. For most gardeners with a greenhouse larger than 6x6 feet, or for anyone growing tender varieties, a digital thermostat is advisable due to its set-and-forget convenience. A manual thermostat is a workable option for a small, budget-conscious setup with uniform, hardy plants, but it requires more hands-on management. Full details in our guide to Electric Greenhouse Heaters With Thermostat.
Understanding running costs
Heating a standard 6x8ft aluminium greenhouse can be expensive, with costs depending heavily on the heater’s wattage and usage time. Electric tubular heaters, designed for continuous use, have very low hourly running costs. In contrast, a 1 kilowatt fan heater is considerably more expensive to operate. Getting a clear picture of these numbers is vital for budgeting your greenhouse heating. Full details in our guide to Running Costs of Greenhouse Heaters UK.
Why heating bills spike in January
High January bills often result from a combination of colder weather and a heater running without a thermostat. Under the October to December 2026 Ofgem price cap, the electricity unit rate is 26.32p per kWh. A 1kW heater running for eight hours each night would cost approximately £14.74 per week. The choice of heater wattage and, crucially, its control mechanism, determines whether the cost remains manageable. Full details in our guide to Running Costs of Greenhouse Heaters UK.
Calculating your specific running cost
You can work out the running cost if you know your electricity tariff. The calculation is: (Heater wattage / 1000) x Hours used x Price per kWh. This simple formula lets you estimate the cost of any heater before you purchase it, helping you avoid an unexpectedly high bill. Full details in our guide to Running Costs of Greenhouse Heaters UK.
Can I leave a tubular heater on all winter?
Yes, electric tubular heaters are built for permanent installation and can be left on throughout winter. Their low wattage means they cost very little to run. They are an economical solution for small spaces where the goal is simply to prevent freezing, accepting that they offer no variable temperature control. For maintaining specific temperatures to protect plants, a thermostatically controlled heater is required. Full details in our guide to Best Greenhouse Heaters for Winter UK.
Is a 1kW heater enough for a 6x4 greenhouse?
A 1kW heater is typically adequate for a small, well-insulated 6x4 greenhouse containing hardy plants, provided it has a thermostat to control runtime. Running such a heater for eight hours a night would result in a weekly cost of around £14-£15, which is often acceptable for a space that size. For larger greenhouses or those housing tender plants, a more powerful unit would be needed. Full details in our guide to Running Costs of Greenhouse Heaters UK.
The risk of using a heater without a thermostat
A heater without a thermostat will run non-stop, which is a costly problem with today’s electricity prices. It cannot maintain a stable temperature, leading to cycles of overheating and cooling that can harm plants. The thermostat is the component that transforms a simple heater into an effective and efficient tool for plant protection. Full details in our guide to Electric Greenhouse Heaters With Thermostat.
Your next steps
The questions on this page fall into two main categories. If your primary concern is choosing the right heater, our guide to Best Greenhouse Heaters for Winter UK provides a detailed comparison. If you’re focused on managing the running costs, then Running Costs of Greenhouse Heaters UK offers the deep dive you need.
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